In commonly owned co-pending U.S. Ser. No. 270,551, filed Nov. 14, 1988, now abandoned, it is proposed to use an alkoxyalkanol solvent to improve the spin coating of metal alkoxide precursors in the fabrication of metal oxide films on a desired substrate. The instant invention is an improvement of using such a technique in the manufacture of high temperature superconductor (HTSC) films;
Various disclosures exist in the scientific literature which are germane to the field of the instant endeavor:
1. G. Moore et al. in Materials Letter, Vol. 7, No. 12, March, 1989, pp. 415-424, discuss the sol-gel technique as it pertains to HTSC films. It discloses the use of yttrium and barium metals dissolved in methoxyethanol and a copper(II) ethoxide compound as the copper source. The heat treatment involves heat treatment in oxygen followed by a longer annealing heat treatment in oxygen as well. Excess barium was volatilized during the heat treatments enabling formation of the desired 1-2-3 phase for the HTSC.
2. European Patent Publication No. 280,292 relates to HTSC manufacture using alkoxides of yttrium and barium with a carboxylate of copper. This patent publication discloses the use of diethylene glycol monomethylether as a solvent in certain of its embodiments. Firing in the atmosphere at elevated temperatures is disclosed.
3. European Patent Publication No. 300,561 also discusses the use of the sol-gel process to form HTSC films using a butanol solvent with yttrium and barium alkoxide and copper cyclohexanebutyrate precursors. Air firing in the temperature range of 175.degree. C. to 900.degree. C. forms an additional important aspect to the process shown in that patent.
4. U.S. Pat. No. 4,943,558 discusses forming HTSC films using a pre-oxygen nitrogen anneal for the HTS films formed on a silicon or silicon dioxide substrate. The annealing does not utilize a water saturated atmosphere in either the nitrogen annealing step or in the later oxygen annealing procedure.